Pins 21 to 24 on new power supplies provide 3 voltages that you already have. Google "ATX power supply pinout" to see these. While it's theoretically possible to make your own auxiliary connector tapping into the existing PS sources, I'd not do that with a marginal power supply. As a rough guess, I'd say you need a PS that specs at 350-400 watts to provide the extra insurance needed to deliver what you actually need. As well, did you check to see if that MB has an additional connection for CPU power. All of the socket 478 MBs I've seen do need that additional power source. Your PS would need a 4 pin connector dedicated to that purpose. I'd have to advise digging up a proper power supply here. It's probable that even your old one no long delivers the current it did when new.
I'm looking at buying a Motherboard 945GCT-HM (Livermore8)/Dual Core E2180 CPU/2Gb DDR2 RAM/ Radeon HD450 PCI-Express from one of my friends. I'll be able to do some simple video editing (windows moviemaker)which my current system(2.66Ghz P4 Socket 478 Northwood, 1Gb DDR400 RAM,128 Mb Radeon 9250, Win XP Home) does not allow. Taps out my CPU AT 100%.
The issue is my PSU.
I've checked on a a lot of PSU calculator sites which say the 280 Watt FSP power supply I have will do the job (Min PSU 222 Watts at extreme.outervision.com for example).In fact there is next to no difference between the current configuration and the proposed. Yeah, yeah I know I'm way under powered by today's standards but I live in New Zealand where things are not so cheap.
The new motherboard has a 24 pin ATX motherboard connector whereas my power supply only as a 20 pin. From what I understand the other four pins supply power to the PCI Express slot? That said it appears from what I've read the 20pin might still work, its just whether it will supply enough power to the PCI-e slot to make the system stable. There's some that say this is only an issue where there is more than one video card. This is where I'm confused. As I plan to buy a new system in the not too distant future I don't want to be shelling out unnecessary money now. Is it worth a try or not? Your views would be appreciated